1. Field of the Invention
The present invention relates to a multi-piece golf ball excellent in flight performance and shot feeling. More particularly it relates to a multi-piece golf ball which retains a low spin inherent in two-piece golf balls, as well as a high trajectory angle at the time of shot, and also has an improvement in shot feeling.
2. Description of the Prior Art
Conventionally thread-wound golf balls and two-piece golf balls are usually employed. In the former, a rubber thread is wound about a core which is a solid rubber ball (solid center) or a liquid-filled spherically shaped rubber envelope (liquid center), and further covered with a cover made of balata or the like. In the latter, a rubber core is covered with a cover made of a thermoplastic resin, e.g., ionomer.
Thread-wound golf balls are excellent in impact at the time of shot (which means good shot feeling) and controllability. However, since they are of structure inherently susceptible to spin, a sufficient flying distance cannot be secured in a wind ahead and they are also poor in durability. As compared with thread-wound golf balls, two-piece golf balls have superior durability and can ensure a flying distance in a wind ahead because they are not susceptible to spin and have a high coefficient of restitution. However, from the standpoint of ensuring high coefficient of restitution, the two-piece golf balls are generally hard and thus inferior in shot feeling to the thread-wound Golf balls.
As a golf ball which has improvements in shot feeling while ensuring the flight performance of two-piece golf balls, a variety of multi-piece golf balls have been proposed which comprise disposing an intermediate layer between a cover and a core, providing two or more layers of covers, providing two or more layers of cores, or a combination of these. Japanese Patent Laid-Open Nos. 33617/1996, 336618/1996, 56848/1997, 248351/1997, 266959/1997 and 299510/1997 disclose multi-piece golf balls excellent in both flight performance and shot feeling which are attained by arranging such that each layer has a hardness in a predetermined range.
The multi-piece golf balls as disclosed in the above publications are broadly classified into three groups: ones in which the outermost layer of a cover is the hardest and a soft layer is provided on the inside of the cover (e.g., 33617/1996); ones in which between a core and a cover there is disposed a core enclosing layer softer than the core (e.g., 336618/1996); and ones in which a core enclosing layer is the hardest (e.g., 266959/1997, 248351/1997).
There are, however, demands on further improvements in shot feeling and flying distance. Particularly, improvement in shot feeling is insufficient depending on the kind of club. For example, even if it is possible to reduce impact upon the shot of a golf ball by a driver or an iron when the cover is hard, the coefficient of restitution increases, but the shot feeling upon use of a putter is poor.
Accordingly, it is a primary object of the present invention to provide a golf ball which offers fine shot feeling with any kind of club, while retaining high coefficient of restitution inherent in solid golf balls.
According to a first aspect of the present invention, a multi-piece golf ball comprises a center core having a JIS-C hardness of not more than 75, a cover having a JIS-C hardness of not less than 85, a core enclosing layer which directly encloses said center core having a JIS C hardness smaller than the others, and a r.d. preventing layer which prevents a restitution coefficient degradation, being internally disposed in contact with said cover and having a JIS C hardness greater than the others.
The multi-piece golf ball of this invention further may comprise an interposing layer between the core enclosing layer and the restitution coefficient degradation preventing layer.
Another aspect of the present invention, a multi-piece golf ball comprises a center core, a core enclosing layer covering the center core, an inner cover layer covering the core enclosing layer, and an outer cover layer covering the inner cover layer. The center core has a JIS-C hardness of from 50 to 75. The core enclosing layer has a JIS-C hardness of less than 50. The inner cover layer has a JIS-C hardness of not less than 97. The outer cover layer has a JIS-C hardness of not less than 85 and less than 97.
The term xe2x80x9cJIS-C hardnessxe2x80x9d used herein is the hardness determined with a spring hardness tester C type according to JIS(Japanese Industrial Standard)-K6301.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.